Exhaust treatment for outboard motor

ABSTRACT

An exhaust system for a marine propulsion outboard drive wherein the exhaust gases are normally discharged to the atmosphere at a point below the level of the body of water in which the watercraft is operating. A catalyst bed is provided in the exhaust system and the catalyst bed is protected from damage by precluding the flow of water in the exhaust conduit to the catalyst bed in response to certain conditions. These conditions may be either rapid deceleration of the engine or watercraft, stopping of the engine, or any of a combination of sensed factors. The water is precluded either by purging it through air pressure or from generating heat in the exhaust conduit, by providing a heat source in the exhaust conduit that will cause water to vaporize and increase the pressure or by a valve in the exhaust conduit positioned below the catalytic bed. The preclusion of water is initiated for only a predetermined time or until the sensed condition no longer is existent.

BACKGROUND OF THE INVENTION

This invention relates to an exhaust treatment for an outboard motor,and more particularly to an improved catalytic exhaust system for suchoutboard motors.

The desirability of effectively controlling the amount of harmfulexhaust gas constituents in internal combustion engines are well known.These goals are particularly desirable in conjunction with outboardmotors wherein the exhaust gases are discharged not directly to theatmosphere but through the body of water in which the associatedwatercraft is operating. As a result of this, not only is there a dangerof air pollution from undesirable exhaust gas constituents but also aproblem in conjunction with possible water pollution.

Although many steps are taken in the basic design of the engine toensure good fuel efficiency and effective exhaust gas treatment, undersome instances it is desirable to also employ catalysts in the exhaustsystem for treatment to reduce certain harmful exhaust gas constituents.As is well known, these catalysts operate at relatively hightemperatures in order to be fully effective, and their efficiencydepends upon their temperature.

As has been previously noted, it is the normal practice in marinepropulsion units to discharge the exhaust gases to the atmospherethrough the body of water in which the watercraft is operating. This isparticularly desirable because most marine propulsion systems do notoffer sufficient space for full engine exhaust silencing. By dischargingthe exhaust gases to the atmosphere through the body of water in whichthe watercraft is operating, further silencing can be obtained.

However, the use of such underwater exhaust gas discharges can presentsome problems, particularly where catalytic exhaust systems areemployed. The water level within the exhaust system can change quiteabruptly during engine operation. For example, when the watercraft istraveling at a high speed and is in a planing condition, the underwaterdischarge and exhaust system is relatively shallowly submerged. Theexhaust gas pressure is high enough so as to ensure that water cannotenter backward through the exhaust system and come into contact with thecatalyst.

If, however, the boat is abruptly decelerated, then the boat and itspropulsion system becomes more deeply submerged in the body of water inwhich the watercraft is operating. In addition, at this time the exhaustpressure falls off, and water can easily flow back into the exhaustsystem through the underwater exhaust gas discharge. If this water comesinto contact with the catalyst, the catalyst may become polluted andinoperative or, alternatively, have its efficiency deteriorated. In aworst case situation, the catalyst bed may actually become shattered ordamaged due to the impacting of water on it at its elevated temperatureand the fact that many catalyst beds are of ceramic-type material. Theseproblems are particularly acute in operating in salt-water environmentsas the salt in the water may offer further fouling of the catalyst.

It is therefore a principal object of this invention to provide animproved exhaust treatment for an outboard motor.

It is a further object of this invention to provide an improvedarrangement for protecting an outboard motor and its catalytic exhaustsystem from damages or inefficiency under all running conditions.

It is a further object of this invention to provide a catalytic exhaustsystem for a marine propulsion unit wherein it would be ensured that thewater through which the exhaust gases are discharged cannot reach thecatalytic bed.

Even in marine exhaust systems that do not include catalytic treatmentin the exhaust gases, there is a desirability to ensure against waterencroaching into the exhaust conduit above a predetermined point. As iswell known, there are times when the exhaust pulses may produce actuallya negative pressure at the discharge end of the exhaust pipe thatconveys the exhaust gases to its underwater exhaust gas discharge. Ifwater can reach this level under such conditions as extremedeceleration, then there is a risk that the water can actually enterinto the engine through its exhaust port. This is obviously undesirable.

It is therefore a still further object of this invention to provide animproved exhaust system for a marine propulsion unit wherein it isensured that water cannot enter the engine through its exhaust ports.

It is a further object of this invention to provide an improved systemfor protecting against undue rise in the water level in the exhaustsystem of an outboard drive.

SUMMARY OF THE INVENTION

This invention is adapted to be embodied in a marine outboard drive thatis comprised of an internal combustion engine having at least oneexhaust port. A drive shaft housing and lower unit is adapted to besupported on the transom of an associated watercraft and has apropulsion device that is driven by the engine for propelling thewatercraft through a body of water. An underwater exhaust gas dischargeis formed in the drive shaft housing and lower unit for dischargingexhaust gases to the atmosphere through the body of water in which thewatercraft is operating. Exhaust conduit means deliver exhaust gasesfrom the exhaust port to the underwater exhaust gas discharge. Means areresponsive to a sensed condition for precluding water flowing above apredetermined position in the exhaust conduit means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic cross-sectional view of an outboardmotor attached to the transom of an associated watercraft (shown onlypartially) and the various components of the system for protecting thecatalytic exhaust system.

FIG. 2 is an enlarged cross-sectional view of the outboard motor portionshown in FIG. 1 and showing in more detail the actual construction.

FIG. 3 is a block diagram showing a control routine in accordance withthe invention.

FIG. 4 is a partially schematic view, in part similar to FIG. 1, andshows another embodiment of the invention.

FIG. 5 is a partially schematic view, in part similar to FIGS. 1 and 4,and shows a still further embodiment of the invention.

FIG. 6 is a partially schematic view, in part similar to FIGS. 1, 4, and5, and shows a further embodiment of the invention.

FIG. 7 is a partially schematic view, in part similar to FIGS. 1, 4, 5,and 6, and shows yet a further embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now in detail to the embodiment of FIGS. 1-3, and initially toFIGS. 1 and 2, an outboard motor constructed in accordance with anembodiment of the invention is identified generally by the referencenumeral 11. The invention is described in conjunction with an outboardmotor because it has particular utility in conjunction with watercraftand the exhaust systems therefor and has particular application withoutboard motors. It should be readily apparent, however, that theinvention may also be used in conjunction with inboard/outboard drivesof the type wherein there is an exhaust system that discharges theexhaust gases from the powering internal combustion engine beneath thebody of water in which the watercraft is operating.

The outboard motor 11 includes a power head assembly, indicatedgenerally by the reference numeral 12, which is comprised of a poweringinternal combustion engine 13 and a surrounding protective cowlingcomprised of a lower tray portion 14 and an upper removable main cowlingportion 15. Although the invention is capable for use with a widevariety of types of internal combustion engines, in the illustratedembodiment, the engine 13 is of the three-cylinder in-line typeoperating on a two-stroke crankcase compression principle. It will bereadily apparent to those skilled in the art, however, that theinvention may be practiced with a wide variety of types of engines. Theinvention does have particular utility, however, in conjunction with twocycle crankcase compression engines because these engines normally arelubricated by lubricant that is not recirculated but is passed throughthe engine and then burned in the combustion chambers and exhaustedthrough the exhaust system. This presents certain problems inconjunction with exhaust emission control.

Some details of the construction of the engine 13 will be describedlater because they are involved in the control strategy.

The engine 13, as is typical with outboard motor practice, is supportedso that its output shaft, a crankshaft 16, rotates about a generallyvertically extending axis. This crankshaft is coupled to a drive shaft17, which depends into a drive shaft housing 18 and is rotatablyjournalled therein in any well-known manner. A lower unit 19 dependsfrom the drive shaft housing 18 and contains a conventional forward,neutral, reverse transmission, indicated generally by the referencenumeral 21 for driving a propeller shaft 22 in selected forward andreverse directions. A propeller 23 has a hub portion 24 that is coupledto the propeller shaft 22 for propelling the associated watercraft,shown partially and indicated generally by the reference numeral 25 in awell-known manner.

A steering shaft 26 is affixed to the drive shaft housing 18 in a knownmanner and is supported for steering movement about a generallyvertically extending steering axis in a swivel bracket 27. A tiller 28is affixed to the upper end of the steering shaft 26 and is coupled toany form of remote steering mechanism or may be steered directly forcontrolling the direction of travel of the associated watercraft 25.

The swivel bracket 27 is, in turn, pivotally connected by means of apivot pin 29 to a clamping bracket 31. This pivotal connection permitstilt and trim movement of the outboard motor 11, as is well known inthis art. The clamping bracket 31 is provided with means, such asthreaded fasteners 32, for a detachable connection to a transom 33 ofthe associated watercraft 25.

Referring now again to the power head 12, although the invention dealsprimarily with the exhaust system, and the internal details of theengine 13 are not particularly essential to the understanding of theinvention, certain components will be described because they incorporatefeatures that present certain control parameters to be measured.

It has been noted that the engine 13 is of the three-cylinder in-linetype that operates on a two-stroke crankcase compression principle. Inthe illustrated embodiments, the engine 13 is mounted in the power head12 so that its crankcase faces forwardly and the cylinder head facesrearwardly. As is conventional with two-cycle engines, an intake aircharge is drawn into the crankcase chambers of the engine 13 through aninduction system. This induction system includes an air intake device34, which is contained with the protective cowling of the power head 12,and specifically within its upper housing portion 15. An air inlet (notshown) is provided in this protective cowling so that atmospheric airmay be drawn into the air inlet device 34 for operation of the engine13. The air inlet device 34 is designed so as to incorporate a silencingsystem for silencing the intake air charge, as is well known in thisart.

The air drawn through the air inlet device 34 is transferred to aplurality of throttle bodies 35 in which throttle valves 36 arepositioned so as to control the speed of the engine 13. The throttlevalves 36 are all linked together by a mechanism so as to besimultaneously operable and operated through any remotely positionedthrottle control in a well-known manner. The air charge is thendelivered to the crankcase chambers of the engine through a suitableinduction system, which includes read-type check valves 37 shownschematically in FIG. 1, which permit the air flow to occur into thecrankcase chambers but prevent reverse flow when the charge is beingcompressed.

Although any form of charge-forming system may be employed inconjunction with the engine 13, in the illustrated embodiment the engineis provided with a fuel injection system that includes fuel injectors38, which receive fuel from a remotely positioned fuel tank, through asupply conduit in which a flow rate sensor 39 is provided. The flow ratesensor 39 outputs its signal to a CPU, indicated generally by thereference numeral 41, which controls, among other things, the amount offuel supplied to the engine by the injectors 38.

The engine 13 is also provided with a spark ignition system, includingspark plugs (not shown) that are fired by the CPU 41 at the appropriatetiming. This ignition system includes a speed sensor 42 of the pulsertype which cooperates with a toothed wheel 43 affixed for rotation withthe crankshaft 16 so as to provide pulses indicative of the rotationalspeed of the engine output shaft 16.

Of course, the fuel injection control and spark ignition control mayinclude other sensors, some of which will be described. Some of thesesensors also are employed in conjunction with the protective system forthe exhaust system, which exhaust system will now be described bycontinued reference to FIGS. 1 and 2.

As shown schematically in FIG. 1, the engine 13 has exhaust ports thatcommunicate with an exhaust manifold 44 that is formed integrally withinthe cylinder block of the engine and which has a downwardly facingdischarge port 45. This discharge port communicates with a correspondingexhaust passage 46 formed in a spacer plate 47 upon which the engine 13is mounted. The spacer plate 47 is supported on the upper side of thedrive shaft housing 18 in a well-known manner. An exhaust pipe 48 isaffixed to the underside of the spacer plate 47 and collects the exhaustgasses and discharges them into a first expansion chamber volume 49formed within the drive shaft housing 18 by an inner shell 51. Ifdesired, the internal surface of the exhaust pipe 48 may be coated witha catalytic material 52 so as to provide some treatment of the exhaustgasses before they are discharged into the first expansion chamber 49.

A vertically extending wall 53 formed within the inner shell 51separates the first expansion chamber 49 from a second expansion chamber54. Exhaust gasses that have flown through the first expansion chamber49 must pass to the second expansion chamber 54 through an area 56formed above the wall 53 so as to form a trap-like construction whichwill assist in ensuring that water cannot flow back through the exhaustsystem to the exhaust ports of the engine under extreme situations andwhen the exhaust protection system, to be described, may malfunction.

At the upper end of the second expansion chamber 54, there is provided acatalyst bed 57 through which the exhaust gasses must pass before theycan exit the second expansion chamber 54 through a downwardly facingdischarge opening 58. Hence, the exhaust gasses that flow through theexhaust system as thus far described will be silenced by successive,contractions through the exhaust pipe 48 and expansion in the expansionchamber 49, subsequent restriction or contraction in the trap section 56and further expansion in the expansion chamber section 54. In addition,the catalyst beds 52 and 57 will treat such exhaust gas constituents asmay be desired, depending upon the design. The specific catalyticmaterials chosen may be of any known type employed in this art.

An exhaust discharge passage 59 is formed in the lower unit 19 andreceives exhaust gasses from the expansion chamber outlet 58. Theseexhaust gasses are then discharged to the atmosphere through the body ofwater in which the watercraft is operating through an underwater exhaustgas discharge. In the illustrated embodiment, this underwater exhaustgas discharge is indicated generally by the reference numeral 61, andthis is of the through-the-hub type, which is discharged through the hub24 of the propeller 23.

In FIGS. 1 and 2, there are depicted three water levels--L1, L2 and L3.The water level L1 is the water level that exists when the watercraft 25is being propelled at a relatively high speed and is in a planingcondition. This water level is just slightly above anti cavitation plate21 of the lower unit 19. Under this running condition, substantially allof the exhaust gasses will be discharged to the atmosphere through thepath as thus far described, including through the through-the-hubunderwater exhaust gas discharge 61.

When the watercraft 25 is operating at a lower than planing speed or isstationary, the water level L2 will be higher. It should be noted thatthe lower end of the exhaust pipe 48 is disposed slightly above thislower water level. Under this condition, the exhaust gas pressure willbe relatively low and not sufficient to exit through the underwaterexhaust gas discharge 61. There is thus provided an above-the-water lowspeed exhaust gas discharge which is formed by a pair of openings 63formed in the expansion chamber forming member 51 and which permit theexhaust gasses to flow out of the expansion chamber section 54 into acavity 64 formed between the outer periphery of the inner shell 51 andthe inner periphery of the drive shaft housing 18. An above-the-waterexhaust gas discharge 65 is formed at the rear of the drive shafthousing 18 so that the exhaust gasses may be discharged through thisopening when the water level is at the level L2. It should be noted thatthe exhaust gasses that are discharged through the opening 65 will havepassed through the entire silencing section of the exhaust system,including the expansion chambers 49 and 54, and past both of thecatalytic beds 52 and 57 so that even though the exhaust gasses aredischarged directly to the atmosphere, they will be silenced andtreated. The opening 65 is relatively restricted, however, so that whentravelling at high speeds, there will be substantially no exhaust gassestransmitted directly to the atmosphere. It should be noted that thisabove-the-water exhaust gas discharge 65 is shown out of position inFIG. 1 for the sake of illustration purposes only.

The engine 13 is water cooled and has a cooling jacket and internal flowpath which may be of any desired type. Water for cooling the engine isdrawn through a water inlet opening 66 formed in the lower unit 19 by awater pump 67 driven from the drive shaft 17 at the interface betweenthe drive shaft housing 18 and the lower unit 19. A conduit 68 extendsfrom the water inlet opening 66 to the water pump 67. This water is thendelivered to the engine cooling jacket through a supply conduit 69 whichextends upwardly through the drive shaft housing 18 and communicateswith the engine cooling jacket in any suitable manner. This coolant isthen discharged downwardly through a cooling jacket 71 formed in thespacer plate 47 around its exhaust passage 46. The coolant is thenfurther delivered to a water jacket formed around the expansion chamberforming inner shell 51 by an inner wall member 72 so as to cool theexhaust system. This water then spills over a weir and is dischargedback into the body of water in which the watercraft is operating throughany known type of discharge.

As has been noted, the highest water level experienced during normalrunning operations is the idle or stationary water level L2. Thecatalyst bed 57 is positioned above this water level and hence isprotected under normal circumstances. However, there is a runningcondition when the water level could reach a higher level, and this iswhen the outboard motor 11 and associated watercraft 25 are travellingat a high speed and then suddenly decelerated. Under this condition, thewater level may actually reach the level L3, and since the exhaust isgenerally open beneath the water, then water could reach the catalystbed 57 and cause damage. This damage could be as severe as shattering ofthe bed due to its high temperature and ceramic nature, or merelyfowling it with the water. If the watercraft 25 is operating in a marineenvironment, then the salt walter could leave deposits on the bed 57that would cause it to lose efficiency. In accordance with an importantfeature of the invention, arrangements are provided in the variousembodiments which ensure that the water level cannot reach a level wherethe bed 57 could be damaged. Alternatively, the protective system maypermit the water level to reach higher points, but only after thetemperature of the bed 57 is low enough that damage would not occur.

In this particular embodiment, the protection is achieved bypressurizing the exhaust conduit and exerting sufficient pressure so asto prohibit the water level from rising, or if the water level hasrisen, to drive the water level back downwardly. This system includes acentrifugal air pump 73 that is mounted on the side of the engine 13within the power head 12 and which is driven by an electric motor 74.The air pump 73 draws air from within the protective cowling through aninlet 75 and discharges it to a conduit 76 in which a check valve 77 ispositioned. This conduit 76 then communicates with a discharge port 78formed in the lower portion of the cylinder block and which communicateswith a further passage 79 formed in the spacer plate 47 thatcommunicates with the expansion chamber section 54 adjacent the trapsection 56 and above the catalyst bed 57.

The electric motor 74 is provided with electrical power from a storagebattery 81 which may be conveniently positioned in the hull of thewatercraft 25 through a pair of conductors 82. An electrically operatedcontrol switch 83, actuated by the CPU 41, controls when the electricmotor 74 and pump 73 are driven. This control strategy will now bedescribed after the various sensors employed in conjunction with thecontrol are described.

The engine speed sensor 42 and fuel flow sensor 39 have already beendescribed. Like those sensors, the sensors employed in conjunction withthe exhaust protection system may also be employed to provide othersignals for control of the running of the engine 13 by the CPU 41. Inaddition to those sensors which will be described, it will be obvious tothose skilled in the art that still other forms of sensors may beemployed for achieving the desired purpose.

The relationship of these sensors in their actual physical locationappears in FIG. 2, while FIG. 1 shows the sensors schematically andtheir relationship with the CPU 41. Referring to these two figures, thesensor system includes a catalyst bed temperature sensor 84 whichcomprises a catalyst temperature sensor system section indicated by thephantom box 85 in FIG. 1. As may be seen in FIG. 2, this temperaturesensor 84 is mounted in the inner shell 51 in proximity to the catalystbed 57 and outputs its signal to the CPU 41.

Since the high water level condition exists primarily due to rapiddecelerations, certain sensors also form a part of a decelerator sensingsection, indicated generally by the reference numeral 86, and whichincludes, in addition to the engine speed sensor 42 and the fuel flowsensor 39, an intake manifold pressure sensor 87 which, as shown in FIG.2, is mounted in the intake manifold of the engine downstream of one ofthe throttle bodies 35. As is well known, during rapid decelerations,the intake manifold pressure will be significantly reduced.

There is also provided an exhaust system pressure sensor 88 which ispositioned at an appropriate location in the exhaust system andparticularly in the area in the expansion chamber section 54 upstream ofthe catalyst bed 57 in the area where the high pressure air is deliveredfrom the conduit 79. A decrease in the pressure in the exhaust systemduring times when the engine is running will be indicative that theengine is running at a slow speed or has stopped.

There is further provided a water level sensor 89 which is positioned inthe expansion chamber 54 but below the catalyst bed 57. When the waterlevel reaches the sensor 89, it will give a signal that will indicatethat the water level is rising above the level L2 and to a point wherethe catalyst bed 57 might well be damaged or fouled.

There is also provided a watercraft speed sensor 91 which basically is apitot tube type sensor that is positioned at the leading edge of thelower unit 91 and which will sense dynamic pressure and, accordingly,watercraft speed. If the watercraft speed has been high and then fallsrapidly, the watercraft speed sensor 91 can indicate a rapiddeceleration condition.

Associated with one of the throttle valves 36 is a throttle valveposition sensor 92, and this provides an output signal indicative ofthrottle valve position. If the throttle valve 36 is held in a fully orlargely opened position and then is closed rapidly, this will be anindication of rapid deceleration and a condition when the watercraft isbeing decelerated rapidly and the high water condition might exist.

The final deceleration sensor comprises an induction airflow sensor 93which may be of the pressure-sensitive type positioned in the crankcasechambers of the engine. As is well known, sensing the crankcase pressureat certain crank angles is a good way of indicating air flow to theengine. If this air flow rate decreases suddenly, this is another goodindication of rapid deceleration.

In addition to these sensors which sense actual engine or boatconditions, there is further provided a deceleration action sensingsection, indicated generally by the reference numeral 94, which includesensors that sense when the operator is taking an action which is likelyto produce sudden decelerations. This may include an engine kill or stopswitch sensor 95 which is positioned remotely in the watercraft hull 25and which is initiated by the operator so as to shut off the engine 13by killing its ignition circuit. If this action is taken when thewatercraft 25 is operating at a high speed, then it can also be assumedthat there will be a sudden deceleration condition.

A further control is a sensor 96 which senses the position of the remoteoperator throttle control. If the operator moves the remote throttlecontrol from a high speed condition to a low speed condition in a shorttime period, then it can be assumed that there is a decelerationcondition present or imminent and protective action can be initiatedpromptly.

There is provided a further control section 97 which determines when theengine is actually stopped and this includes an engine stop sensor 98indicates when the engine has been stopped. This may be done bymeasuring lack of rotation of the crankshaft 16, disabling of theignition circuit, etc.

There is provided a further sensor section which is the exhaust passageinternal water level sensor system indicated by the reference numeral 99and this may include a float type device for providing a signalindicative of the actual water level in the exhaust system or in thedrive shaft housing 18, which will in essence be the same.

All of these signals from the sensors described are transmitted to theCPU 41 so as to provide an indication of when protective action isrequired and how that protective action is initiated. This will bedescribed later by reference to a control routine shown in FIG. 3.However, these are transmitted to an engine exhaust pressure increasingsystem, indicated generally by the reference numeral 101 in FIG. 5 andwhich includes an actuating circuit 102 for operating any of a pluralityof pressure increasing systems, one of which is shown in detail in FIG.2 and the others of which will be described later. This actuatingcircuit 102 is powered by the battery 81 and controls either a blowermotor 74 as in the embodiment of FIGS. 1-3, an electric heater to bedescribed later by reference to certain other embodiments, or an airvalve, which will also be described later. Alternatively, several or allof these pressure increasing systems can be employed.

A control routine for protecting the catalyst is depicted in FIG. 3 andwill now be described in detail by reference to that figure. Thiscontrol routine may be employed with any system for precluding waterfrom reaching the catalyst bed 57 and in the specific embodimentillustrated, this is accomplished by turning on the blower motor 74 andblower 73 so as to pressurize the expansion chamber section 54 and forceany water which may be rising in this expansion chamber back downwardlyinto the body of water in which the watercraft is operating through theunderwater exhaust gas discharge system already described. As willbecome apparent by description of the remaining embodiments, othermethods may be employed for protecting the catalyst bed 57 from thewater. In addition, FIG. 3 illustrates the measuring of only certainparameters and as has been previously discussed and as will be repeated,various other parameters can be sensed so as to determine when it isdesirable to initiate protective action.

The program starts and moves to the first step S1 wherein the mainswitch for the control of the outboard motor 11 initiated by theoperator. The engine control routine then is automatically switched onat the step S2 and certain values are read at the step S3. These valuesare indicated as A.

In this embodiment, four values of A are read. These are engine speed A1(Ne), intake manifold pressure A2 (Pi), exhaust pipe pressure A3 (Pe)and water level height A4 (H). From the values of engine speed, intakemanifold pressure and exhaust pipe pressure, it may be determined thatnot only whether the engine is running, but also if it has beendecelerated rapidly. In the case that the engine 13 has been stopped ordecelerated rapidly, there is a condition when the water level may risefrom the level L1 to the level L2 or even to the higher level L3 andprotective action may be desired. Stopping of the engine can bedetermined if either engine speed has gone to zero or if intake manifoldpressure or exhaust pipe pressure becomes atmospheric pressure. Rapiddeceleration can be determined if engine speed decreases by more than apredetermined amount in a predetermined time period or if intakemanifold pressure or exhaust pipe pressure change by more than apredetermined amount in a predetermined time period. As has beenpreviously noted, a rapid increase in intake manifold vacuum or decreasein intake manifold pressure will indicate an extreme decelerationcondition and a rapid decrease in exhaust pipe pressure will alsoindicate a rapid deceleration.

After the values of A have been read, the program then moves to the stepS4 to compare the values with the predetermined values at B which areindicative of the deceleration or stop condition. In the embodimentillustrated in FIG. 3, the determination is made as to whether theengine has stopped and thus, B1, B2 or B3 values of Ne, Pi or Pe equalszero, it will be determined that the engine has stopped. Insofar asdetermining the other condition of protection of the water level heightH, if the water level height H is read at B4 as greater than a specifiedvalue, then it will be determined that protective action may berequired.

In the control routine described in FIG. 3, protective action is notautomatically initiated in the event the B value is read by the system.In accordance with this control routine, it is determined thatprotective action is not required unless the catalyst temperature isgreater than a predetermined temperature. Catalyst temperature isindicated as T_(s) and if this temperature is greater than apredetermined value and the condition B is met, then protective actionwill be initiated.

Therefore, at the step S5, the temperature of the catalyst is read andat the step S6 it is determined if the catalyst temperature is highenough as to require protective action. If at the step S6 it isdetermined that the temperature is too high, the program then moves tothe step S7 so as to switch on and begin the protective action. In thisembodiment, this condition is initiated by the CPU 41 switching on theswitch 83 so as to activate the electric motor 74 and blower 73 so as toturn on the protective action and begin forcing water out of the exhaustsystem by pressurizing the expansion chamber section 74.

If at the step S4 it is determined that none of the read values of A arethe values of B which require protective action or if it is determinedat the step S6 that the catalyst temperature is not too high, then theprogram moves to the step S8 so as to determine if a previouslyinitiated pressurization action is still being initiated. Thepressurization action may have been initiated because of a previouscondition when the value of B had been met and the temperature of thecatalyst bed was too high. However, assuming that now the value of B isnot that which requires protective action and/or the temperature of thecatalyst bed was not too high and it is then determined at the step S8that the protective action had been initiated, the program then moves tothe step S9 so as to deactivate the protective action since it is nolonger required. The program then moves to the step S10 to determine ifthe main switch is still on.

If at the step S10 it is determined that the main switch is still on,the program then moves back to the step S3 so as to continue to monitorthe conditions to determine if protective action is subsequentlyrequired. If, however, at the step S10 it is determined that the mainswitch has been turned off, then the program moves to the step S11 so asto turn off the engine control and then the program ends.

If at the step S8 it has been determined that the protective action isno longer being initiated, the program then jumps to the step S10 todetermine the condition of the main switch. If the main switch is stillon at the step S10, the program repeats back to the step S3 to continueto monitor conditions to determine if protective action is subsequentlyrequired. If, at the step S10 it is determined that the main switch hasbeen turned off, then the engine control is again turned off at the stepS11 and the program ends.

As has been noted, this control routine is only one of many which can beemployed to practice the invention. In this control routine, theprotective action is begun when one of the sensed conditions, in thiscase, engine stop is determined although as has been noted, the sensecondition can also be a rapid deceleration. However, even the existenceof this condition will not initiate protective action unless thecatalyst temperature is high. Of course, it may be possible to initiateprotective action even if the catalyst temperature is not desired to bedetermined or, alternatively, the protective action can be initiatedimmediately if the catalyst temperature is determined to be too high.Also, the protective action is stopped when both conditions no longerexist. It may be possible to stop the protective action only when thecatalyst temperature falls below a predetermined temperature or when thewater level is below the predetermined water level or, alternatively,there may be a time delay where it is necessary for the two conditionsor one of the conditions not to exist for more than a predetermined timebefore the protective action is discontinued. In addition, it is alsopossible to provide an arrangement wherein the protective action is onlyinitiated for a predetermined time period and then the program againrepeats to determine if new or continued protective action is requiredbecause the condition still call for it. These are only some of manytypes of control routines that can be employed and it will be obvious tothose skilled in the art how such other control routines may bepracticed.

It has also been noted that other means may be provided so as to eitherdrive the water level down in the exhaust conduit downstream of thecatalyst bed 57 and FIG. 4 shows such another embodiment. Since thisembodiment differs from the previously described embodiment only in theway in which this protective action is achieved, only a schematic viewis believed necessary to permit those skilled in the art to understandhow this embodiment is constructed and can be operated.

In this embodiment, the protective action is initiated by raising thepressure in the expansion chamber 49 and the expansion chamber 54 andthis is done by an electrical heater 151 which, in this embodiment, isdisclosed as being in the expansion chamber section 49. The electricheater 151 is provided with a power source such as a battery 152 thatmay be contained within the power head 12 and actuated by a system asshown schematically in FIG. 1 wherein this electric heater is alsoindicated by the reference numeral 151 as a separate type of protectivedevice.

When protective action is required, and this may be sensed in any of thepreviously described methods, the electric heater 151 is energized fromits power source 152 and the expansion chambers 49 and 54 will beheated. This will cause a pressure rise in the exhaust system which willforce the water level downwardly and drive the water out of theexpansion chamber 54 and away from the catalyst bed 57 in a manner whichshould be readily apparent to those skilled in the art.

FIG. 5 shows another embodiment of the invention which generally has thesame overall construction of the outboard motor as the previouslydescribed embodiment. For that reason, this embodiment is illustrated inschematic form and components which are the same or substantially thesame as those previously described have been identified by the samereference numerals. This embodiment uses a source of high pressure airfor purging the exhaust system of excess water under any of theaforenoted conditions. In this embodiment, however, the excess air isprovided by an air compressor 201 which has a pulley 202 driven from theengine crankshaft 16 in a well-known manner. This air compressor chargesan accumulator chamber 203 that is positioned in the power head 12within the main cowling portion 15. A pressure responsive valve 204 inthe line between the air compressor 201 and the accumulator 203determines the amount of pressure at which the accumulator 203 ischarged. A conduit 205 connects the accumulator chamber 203 with theexhaust system and in this embodiment, that connection is to theexpansion chamber section 49. An automatically operated valve 206 isinterposed in the conduit 205 and is open when any of the aforenotedconditions are sensed which would require purging of the exhaust systemfrom water and is closed after the purging action has been completed.Since these various control routines have already been described,further description of them is believed to be unnecessary.

In order to permit the operator to depressurize the accumulator chamber203 at such time as the outboard motor 11 is to be stored or otherwiseserviced, a manually operated valve 207 is provided within theprotective cowling 15 and can be opened by the operator so as todepressurize the system.

FIG. 6 shows another embodiment which is generally similar to theembodiment of FIG. 5 and, for that reason, components of this embodimentwhich are the same as that embodiment have been identified by the samereference numerals. Again, because of the similarity of this embodimentto those previously described, only a schematic view of this embodimentis believed to be necessary to permit those skilled in the art topractice the invention. In this embodiment, rather than having anoperator-controlled valve for depressurizing the accumulator chamber 203and in order to improve performance of the catalytic bed 57, excess airis supplied to the exhaust system upstream of the catalyst bed 57through a further conduit 251 in which a pressure responsive valve 252is provided. The valve 252 permits a small amount of air to be bled intothe expansion chamber section 49 upstream of the catalyst bed 57 at alltimes. This air pressure is not adequate to preclude water level risingsignificantly and the conduit 205 and valve 206 are provided for thatpurpose. However, the air delivered through the conduit 251 is adequateso as to ensure that there will be adequate oxygen for the catalyst bed57 to operate satisfactorily. Also, when the outboard motor 11 is shutdown, the conduit 251 and valve 252 will act as an air bleed so as topermit the pressure in the accumulator chamber 203 to be graduallyrelieved.

FIG. 7 shows another embodiment of the invention and this embodimentincludes a device wherein it is unnecessary to provide a separatedeceleration sensor and the device incorporates in its exhaust system aheat storage device, indicated generally by the reference numeral 301which is positioned downstream of the catalyst bed 57 and above theabove water exhaust gas discharge 65 in the exhaust system. This heatstorage device 301 is adapted to store heat for a long period of timeand may be of any suitable material. When the outboard motor 11 israpidly decelerated or shut off, water will rise in the conduit to theheat storage section 301 and the water will be converted into steamwhich will expand and raise the pressure in the exhaust conduit so as todrive further water downwardly away from the catalyst bed 57. This steamis indicated schematically at 302. The heat storage device 301 isobviously porous so as to let the exhaust gases flow freely through thesystem but also is capable of storing sufficient heat so as to generatesteam for a long enough period of time so as to ensure that the waterlevel can return to normal even under extreme deceleration or rapid shutoff condition so as to protect the catalyst bed 57.

As opposed to the various water purging devices which have been shown,it is also possible to provide some form of valve in the exhaust systemdownstream of the catalyst bed 57 which will shut off under extremedeceleration condition so as to preclude water from rising in theexhaust system and damaging the catalyst bed 57. Such a valve in shownschematically at 351 in FIG. 1. As has been noted, any known type ofvalve assembly can be implied for shutting off the exhaust system andprecluding water from rising to a level sufficient to reach the catalystbed 57.

It should be readily apparent in the foregoing description that thedescribed embodiments of the invention are extremely effective inprotecting the catalyst bed from water damage or water fowling underconditions such as extreme deceleration or engine shut off whentravelling forwardly. Of course, the described embodiments of theinvention are only examples of ways in which the catalyst bed can beprotected and various changes in modifications may be made withoutdeparting from the spirit and scope of the invention, as defined by theappended claims.

We claim:
 1. A marine outboard drive comprising an internal combustionengine having at least one exhaust port, a drive shaft housing and lowerunit adapted to be supported upon the transom of an associatedwatercraft and having a propulsion device driven by said engine forpropelling said watercraft through a body of water, an underwaterexhaust gas discharge formed in said drive shaft housing and lower unitfor discharging exhaust gases to the atmosphere through the body ofwater in which said watercraft is operating, exhaust conduit means fordelivering exhaust gases from said exhaust port to said underwaterexhaust gas discharge, and purging means responsive to a condition forprecluding water from flowing above a predetermined position in saidexhaust conduit means by purging water from said exhaust conduit means.2. A marine outboard drive comprising an internal combustion engine asset forth in claim 1, wherein the means for purging water comprisesmeans for supplying air under pressure to the exhaust conduit means forpurging water therefrom.
 3. A marine outboard drive comprising aninternal combustion engine as set forth in claim 2, wherein the airpressure is provided by an air pump.
 4. A marine outboard drivecomprising an internal combustion engine as set forth in claim 3,wherein the air pump is selectively driven by an external power source.5. A marine outboard drive comprising an internal combustion engine asset forth in claim 3, wherein the air pump charges an accumulatorchamber that supplies air to the exhaust conduit means.
 6. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 5, wherein the accumulator chamber provides a first relatively lowsupply of air to the exhaust conduit means under all running conditionsand a substantially greater supply of air to purge the water from theexhaust conduit means.
 7. A marine outboard drive comprising an internalcombustion engine as set forth in claim 1, wherein the purging meanscomprises a source of heat in the exhaust conduit means.
 8. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 7, wherein the source of heat is selectively applied to theexhaust conduit means.
 9. A marine outboard drive comprising an internalcombustion engine as set forth in claim 7, wherein the source of heatcomprises a heat retaining member.
 10. A marine outboard drivecomprising an internal combustion engine as set forth in claim 1,wherein the marine outboard drive comprises an outboard motor and theengine is positioned in a power head disposed above the drive shafthousing and lower unit.
 11. A marine outboard drive comprising aninternal combustion engine as set forth in claim 1, further including acatalyst bed disposed in the exhaust conduit means for treating theexhaust gases flowing there through and wherein water is precluded fromreaching the catalyst bed in response to the condition.
 12. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 11, wherein the means for purging water comprises means forsupplying air under pressure to the exhaust conduit means for purgingwater therefrom.
 13. A marine outboard drive comprising an internalcombustion engine as set forth in claim 12, wherein the air pressure isprovided by an air pump.
 14. A marine outboard drive comprising aninternal combustion engine as set forth in claim 13, wherein the airpump is selectively driven by an external power source.
 15. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 13, wherein the air pump charges an accumulator chamber thatsupplies air to the exhaust conduit means.
 16. A marine outboard drivecomprising an internal combustion engine as set forth in claim 15,wherein the accumulator chamber provides a first relatively low supplyof air to the exhaust conduit means under all running conditions and asubstantially greater supply of air to purge the water from the exhaustconduit means.
 17. A marine outboard drive comprising an internalcombustion engine as set forth in claim 11, further including means forsensing the condition.
 18. A marine outboard drive comprising aninternal combustion engine as set forth in claim 17, wherein the sensedcondition comprises a water level in the exhaust conduit means.
 19. Amarine outboard drive comprising an internal combustion engine as setforth in claim 18, wherein the sensing means comprises a water levelsensor positioned in the exhaust conduit means.
 20. A marine outboarddrive comprising an internal combustion engine as set forth in claim 17,wherein the sensed condition comprises deceleration.
 21. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 20, wherein the sensed deceleration comprises watercraftdeceleration.
 22. A marine outboard drive comprising an internalcombustion engine as set forth in claim 21, wherein the watercraftdeceleration is determined by a watercraft speed sensor.
 23. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 20, wherein the deceleration comprises deceleration of the engine.24. A marine outboard drive comprising an internal combustion engine asset forth in claim 23, further including a throttle valve forcontrolling the speed of the engine and wherein the sensed decelerationis determined by rapid closure of the throttle valve.
 25. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 23, wherein the sensed deceleration of the engine is determined byan air flow sensor.
 26. A marine outboard drive comprising an internalcombustion engine as set forth in claim 23, wherein the sensed enginedeceleration is sensed by sensing intake manifold vacuum.
 27. A marineoutboard drive comprising an internal combustion engine as set forth inclaim 20, wherein the sensed deceleration is determined by measuring theengine speed and determining when engine speed rapidly is decreased. 28.A marine outboard drive comprising an internal combustion engine as setforth in claim 17, wherein the sensed condition is catalytic bedtemperature.
 29. A marine outboard drive comprising an internalcombustion engine as set forth in claim 17, wherein the sensed conditionis the stopping of the engine.
 30. A marine outboard drive comprising aninternal combustion engine as set forth in claim 11, further includingmeans for discontinuing the preclusion of water from flowing above thepredetermined position after the water has been precluded from flowingabove the predetermined position.
 31. A marine outboard drive comprisingan internal combustion engine as set forth in claim 30, wherein thestopping of the preclusion is done after a predetermined time.
 32. Amarine outboard drive comprising an internal combustion engine as setforth in claim 30, wherein the stopping of the precluding of the waterfrom flowing above the predetermined position is initiated after thesensed condition is no longer present.
 33. A marine outboard drivecomprising an internal combustion engine as set forth in claim 30,wherein the stopping of the preclusion of water is done after thetemperature of the catalyst falls below a predetermined level.
 34. Amarine outboard drive comprising an internal combustion engine as setforth in claim 30, wherein the stopping of the preclusion is after thewater level falls below a predetermined water level.
 35. A marineoutboard drive comprising an internal combustion engine having at leastone exhaust port, a drive shaft housing and lower unit adapted to besupported upon the transom of an associated watercraft and having apropulsion device driven by said engine for propelling said watercraftthrough a body of water, an underwater exhaust gas discharge formed insaid drive shaft housing and lower unit for discharging exhaust gases tothe atmosphere through the body of water in which said watercraft isoperating, exhaust conduit means for delivering exhaust gases from saidexhaust port to said underwater exhaust gas discharge, and meansresponsive to a condition for precluding water from flowing above apredetermined position in said exhaust conduit means comprising a valvepositioned at the predetermined position in the exhaust conduit meansbetween said exhaust port and said underwater exhaust gas discharge. 36.A marine outboard drive comprising an internal combustion engine as setforth in claim 35, further including a catalyst in the exhaust conduitmeans between the exhaust port and the valve, whereby the valveprecludes water from reaching the catalyst.
 37. A marine outboard drivecomprising an internal combustion engine having at least one exhaustport, a drive shaft housing and lower unit adapted to be supported uponthe transom of an associated watercraft and having a propulsion devicedriven by said engine for propelling said watercraft through a body ofwater, an underwater exhaust gas discharge formed in said drive shafthousing and lower unit for discharging exhaust gases to the atmospherethrough the body of water in which said watercraft is operating, exhaustconduit means for delivering exhaust gases from said exhaust port tosaid underwater exhaust gas discharge, means for sensing a condition,and means responsive to the sensing of the condition for precludingwater from flowing above a predetermined position in said exhaustconduit means, said sensed condition comprising a water level in theexhaust conduit means.
 38. A marine outboard drive comprising aninternal combustion engine as set forth in claim 37, wherein the sensingmeans comprises a water level sensor positioned in the exhaust conduitmeans.
 39. A marine outboard drive comprising an internal combustionengine having at least one exhaust port, a drive shaft housing and lowerunit adapted to be supported upon the transom of an associatedwatercraft and having a propulsion device driven by said engine forpropelling said watercraft through a body of water, an underwaterexhaust gas discharge formed in said drive shaft housing and lower unitfor discharging exhaust gases to the atmosphere through the body ofwater in which said watercraft is operating, exhaust conduit means fordelivering exhaust gases from said exhaust port to said underwaterexhaust gas discharge., means for sensing a condition, and meansresponsive to the sensing of the condition for precluding water fromflowing above a predetermined position in said exhaust conduit means,said sensed condition comprising deceleration.
 40. A marine outboarddrive comprising an internal combustion engine as set forth in claim 39,wherein the sensed deceleration comprises watercraft deceleration.
 41. Amarine outboard drive comprising an internal combustion engine as setforth in claim 40, wherein the watercraft deceleration is determined bya watercraft speed sensor.
 42. A marine outboard drive comprising aninternal combustion engine as set forth in claim 39, wherein thedeceleration comprises deceleration of the engine.
 43. A marine outboarddrive comprising an internal combustion engine as set forth in claim 42,further including a throttle valve for controlling the speed of theengine and wherein the sensed deceleration is determined by rapidclosure of the throttle valve.
 44. A marine outboard drive comprising aninternal combustion engine as set forth in claim 42, wherein the senseddeceleration of the engine is determined by an air flow sensor.
 45. Amarine outboard drive comprising an internal combustion engine as setforth in claim 42, wherein the sensed engine decelevation is sensed bysensing intake manifold vacuum.
 46. A marine outboard drive comprisingan internal combustion engine as set forth in claim 42, wherein thesensed deceleration is determined by measuring the engine speed anddetermining when engine speed rapidly is decreased.
 47. A marineoutboard drive comprising an internal combustion engine having at leastone exhaust port, a drive shaft housing and lower unit adapted to besupported upon the transom of an associated watercraft and having apropulsion device driven by said engine for propelling said watercraftthrough a body of water, an underwater exhaust gas discharge formed insaid drive shaft housing and lower unit for discharging exhaust gases tothe atmosphere through the body of water in which said watercraft isoperating, exhaust conduit means for delivering exhaust gases from saidexhaust port to said underwater exhaust gas discharge, means for sensinga condition, and means responsive to the sensing of the condition forprecluding water from flowing above a predetermined position in saidexhaust conduit means, said sensed condition comprising the initiationof stopping of the engine.
 48. A marine outboard drive comprising aninternal combustion engine having at least one exhaust port, a driveshaft housing and lower unit adapted to be supported upon the transom ofan associated watercraft and having a propulsion device driven by saidengine for propelling said watercraft through a body of water, anunderwater exhaust gas discharge formed in said drive shaft housing andlower unit for discharging exhaust gases to the atmosphere through thebody of water in which said watercraft is operating, exhaust conduitmeans for delivering exhaust gases from said exhaust port to saidunderwater exhaust gas discharge, means for sensing a plurality ofconditions, and means responsive to the sensing of any one of saidplurality of conditions sensed for precluding water from flowing above apredetermined position in said exhaust conduit means in response to thesensing of any of said conditions.
 49. A marine outboard drivecomprising an internal combustion engine as set forth in claim 48,wherein one of the conditions comprises water level in the exhaustconduit means.
 50. A marine outboard drive comprising an internalcombustion engine as set forth in claim 48, wherein one of theconditions sensed is engine speed deceleration.
 51. A marine outboarddrive comprising an internal combustion engine as set forth in claim 48,wherein one of the sensed conditions comprises deceleration of theassociated watercraft.
 52. A marine outboard drive comprising aninternal combustion engine as set forth in claim 48, wherein one of thesensed conditions comprises stopping of the engine.
 53. A marineoutboard drive comprising an internal combustion engine having at leastone exhaust port, a drive shaft housing and lower unit adapted to besupported on the transom of an associated watercraft and having apropulsion device driven by said engine for propelling said watercraftthrough a body of water, an underwater exhaust gas discharge formed insaid drive shaft housing and lower unit for discharging exhaust gases tothe atmosphere through the body of water in which the watercraft isoperating, exhaust conduit means for delivering exhaust gases from saidexhaust port to said underwater exhaust gas discharge, and meansresponsive to a condition for precluding water from flowing above apredetermined position in said exhaust conduit means by providing asource of heat in said exhaust conduit means.
 54. A marine outboarddrive comprising an internal combustion engine as set forth in claim 53,wherein the source of heat is selectively applied to the exhaust conduitmeans.
 55. A marine outboard drive comprising an internal combustionengine as set forth in claim 53, wherein the source of heat comprises aheat retaining member.